Rectification column



Jan. 14, 1969 R. BECKER RECTIFICATION COLUMN Sheet Filed Oct. 18. 1966RUDOLF BECKER lXVllYTU/Q RIUKS a Aitomey Sheet Jan. 14, 1969 R. BECKERRECTIFICATION COLUMN Filed Oct. 1a. 1966 RUDOLF BECKER ].\'\'E4\"TORAfton: e y

United States Patent 51,951 U.S. 01. 62-42 Int. Cl. Fj 3/02 6 ClaimsABSTRACT OF THE DISCLOSURE A rectification column having a greaterhorizontal dimension than its vertical dimension and provided with anarray of thick and thin vertically spaced rectification plates withthroughgoing openings allowing the passage of gas and liquid between thestages. The housing of the column has a pair of vertical Walls which arespanned by the thicker plates constituting reinforcing members welded tothe walls along respective horizontal lines while the thin plates aredisposed between the thick plates. Along its exterior, the walls areformed with outwardly convex metal strips joined to the structure at theseams at which the thicker plates are welded to the walls.

My present invention relates to a rectification column of thehorizontal-plate type wherein the plates are vertically spaced and, moreparticularly, to an improved compact column for the refluxing andseparation components of a fluid stream, preferably in cryogenicapplications.

The conventional rectification column is circular in cross section witha vertical height usually considerably greater than the diameter. Thediameter is frequently determined by the allowable transport clearance(e.g. the width of a freight car or diameter of a tunnel) and is,consequently, relatively small. The plates are substantially of the samediameter as the inside of the column, horizontally disposed and axially(i.e. vertically) aligned. Since the space between the plates preferablyis, as determined empirically, an inverse function of the fourth powerof the diameter, conventional columns of small diameter havecorrespondingly large plate spacings and consequently relatively greatheight.

This height has the disadvantage that operating costs are great due tothe hydrostatic heads involved in the pumping of liquids; the smalldiameter results in high gas velocities and relatively deep depth ofliquid retained on the plates, both factors contributing to a highpressure drop and loss of energy in fluid circulation.

Further columns of heights exceeding that permissible on conventionaltransport means necessitate fabrication in parts, increasing fabricationcosts and field-erection expense.

It is an object of the present invention to obviate these ditficulties.

This is accomplished, according to the invention, by making theprincipal axis of the rectification column horizontal and by mountingthe plates parallel to this axis, the plates conforming to thehorizontal cross section of the interior of the column as .atorestated.By so doing, not only is it possible to locate the plates surprisinglyclose together, but-even more surprisinglythe length of the horizontalcolumn is less than the height of the vertical column for the samecapacity, as will be demonstrated hereinafter. Transport problems arenow minimized and field erection greatly simplified.

Further the gas velocities and pressure drop over the column accordingto the present invention are advantageously reduced, resulting in loweroperating costs.

The above objects, advantages and features of my present invention willbecome more readily apparent from the following detailed description,reference being made to the accompanying drawing in which:

FIG. 1 is a side view in perspective, partially cut away;

FIG. 2 is a detail of the head plate of FIG. 1 drawn to a larger scale;and

FIGS. 3 and 4 are side views, in perspective, similar to FIG. 1 butillustrating other embodiments of the invention.

In the drawing I show a housing 1 including generally flat vertical sidewalls 16, one of which is visible, generally flat vertical heads 10, anupper arched hood 17 and a lower arched hood 17', this housing beingsubstantially a rectangular prism with a horizontal longitudinal axis.Tie rods 4, resisting internal thrusts, penetrate side walls 16 and arelocked thereto by nuts or the like.

A plurality of horizontal, rectangular plates, 8a and 8b, axiallyextending and conforming in outline to horizontal sections of housing 1are vertically spaced. apart therein, each plate being provided with amultiplicity of openings 7, the openings of adjacent plates beingstaggered longitudinally and transversely in the respective horizontalplanes. Certain plates 8a are load-bearing plates contributing to thestructural rigidity of housing 1 and have a rigid fastening 12, usuallya weld, joining them to the heads 10. To further reinforce, thegenerally flat vertical heads 10, a plurality of arched (inwardlyconcave) members 11 connect the fastening means 12 at heads 10 at thejunctures with plates 8a as is particularly portrayed in FIG. 2.Openings 9 are provided in web plates 10' which span the junctures forpressure equalization between the rectification stages defined betweenthe plates.

Between plates 8a are one or more intermediate plates 8b which are notstructurally attached to the heads and have lesser thicknesses thanplates 8a; the intermediate plates are suspended therefrom by hangerassemblies 19.

At least two connections for inlet and outlet, 2 and 3 respectively, areprovided, together with at least one intermediate reflux connection 18as is common in conventional rectification columns.

FIG. 3 shows another embodiment in which the housing comprises acylindrical shell 15 with dished heads 13. Interior plates 8, which maybe identical with one another, are shaped at the ends 8' to conform tothe curvature of dished heads 13. The inlet and outlet and the slotscommunicating between stages are otherwise identical with thoseillustrated in FIG. 1, and

FIG. 4 shows still another embodiment in which the housing comprises asquare shell 19, being otherwise identical with FIG. 1.

The compact shape of the rectifying column in the present invention, ashas been heretofore described, permits the convenient pairing of thisunit on a common mounting with an evaporator or plate heat-exchanger ofsimilar profile to the rectification column. Such a com panion unit 14is shown in FIG. 1 in dotted lines, and

can be connected to the rectification column in a conventional mannerknown to the art with a minimum of piping. The unit 14 may be of thetype described in my Patent No. 3,256,704, granted June 21, 1966.Moreover, direct-heat exchange through the housing walls is possible.

The operation of the cryogenic rectification column (e.g. in aLinde-Frankl air-rectification process) is in accord with conventionalpractice, with variation as dictated by the requirements of the fluidsto be fractionated. Basically, a vapor from an evaporator 14 is admittedin the lower section of the column through the inlet 3 and a liquidphase is introduced at a higher level between plates through the inlet18, to flow countercurrent to the rising vapor phase, a vapor-enrichingexchange taking place through liquid-vapor contact on the plates 8n and8b and at the openings 7. The latter may be flanked by downwardlyextending fianges 7' reaching close to the surface of the next lowerplate and bent from the sheet metal contituting the respective plate.The vapor phase is removed, for instance, through connection 2 and theliquid phase is removed or returned to the evaporator through 3 whichmay serve commonly as a vapor inlet and liquid outlet.

An additional advantage of the horizontal and substantially rectangularplates is that the inactive surface in the interchange of gases andliquids is reduced from that of the vertical column plates which aregenerally circular. Circular plates are known to have between 20% to 35%of the plate surface lot through dead peripheral wall junction andnon-mixing zones at the bubble caps. The present invention with thelarger rectangular plates has approximately only 5% in active surface.

Total space is reduced since not only is the profile of the equipmentlower, but the length of the horizontal column is less than the heightof an equivalent vertical column, as is made evident by the followingexample in which it is shown that the length of equivalent columns maybe reduced by one-half in the present invention.

It is seen from the foregoing that, in accord with the presentinvention, this operation is more advantageously carried out than withconventional vertical rectification columns. For an equal loading, therectification column according to the present invention is much lower inheight that is otherwise the case, and hence the hydrostatic headagainst which a liquid-phase feed pump must work is greatly reduced.

EXAMPLE Present practice dictates that the plate-surface area F variesinversely as the square root of the plate spacing H,

a relationship which may be expressed as:

K F t and, where Fv and Fh, are the plate areas of a vertical andhorizontal column respectively and Hv and Hh. are the plate spacings ofsuch columns, respectively, it can be seen that Thus with a horizontalcolumn in accord with the present invention wherein the length is 5.5m., width 3.6 m., and having 25 plates set 0.10 m. apart, it will beevident that there are 24 interplate spaces at 0.10 m., a total of 2.4m., to which must be added top and bottom gas passage spaces under thehoods of 0.6 m. each, giving a total height of 3.6 m., thereby definingthe dimensions of the rectifier. Best results are obtained with aninterplate spacing, for all rectifiers, according to the inventionhaving horizontal longitudinal axes of 80 to 200 mm. and preferablyabout 100 mm.

For purposes of comparison, a conventional vertical column 3.6 m. indiameter may be hypothesized. Such a column will have plate areas of10.2 m. as compared to the plate area of 19.8 m? for the horizontalcolumn. Now, employing the relationship (2) above:

whence 1112:04 m.

Now, 24 spaces at 0.4 m. requires 9.6 m. height, plus 1.2 111. each forthe conventional vertical still head and foot, gives a total height of12 m. for the vertical cylindrical rectification column of conventionaldesign. Such columns commonly require an interplate spacing of at least300 mm. and may have spacing ranging to 600 mm.

It is seen in the above example that not only is the height rediced 8.4m. by use of the invented column, but the overall length, important inshipping, is reduced by 6.5 In.

My invention has been illustrated in a single example embodiment whichis in no way restrictive. Those skilled in the art can make numerousrevisions according to design preferences; such revisions are, ofcourse, included within the spirit and scope of the appended claims.

I claim:

1. A rectification column comprising: an elongated housing having ahorizontal longitudinal axis, an array of parallel horizontal firstplates extending parallel to said axis, spaced apart within said housingand conforming in shape to the interior cross-section thereof, saidfirst plates being provided with openings communicating between theinterplate spaces of said array; inlet means for admitting a gas and aliquid into said housing for rectification therein; outlet means forremoving gas and liquid from said housing; said housing including anarched upper hood spaced above said array and an arched lower hoodspaced below said array to permit passage of a gas and a liquidtherebet-ween, a pair of axially extending, parallel side walls,transverse tie rods connecting said side walls, and end walls transverseto said longitudinal axis, said first plates being rigidly fastened tosaid end walls; parallel horizontal intermediate plates axiallyextending and vertically spaced between said first plates, saidintermediate plates being provided with openings for passage of said gasand liquid therebetween, said end walls being reinforced with archestransverse to saidt axis and bridging said first plates while beingrigidly fastened in common with said first plates at said end plates,said end walls being provided with pressure-equalizing ports openinginto chambers formed between said end walls and each of said arches.

2. A rectification column defined in claim 1 wherein said first platesand said intermediate plates are substantially rectangular.

3. A rectificzation column as defined in claim 1 wherein said plates areseparated by a vertical distance of to 200 mm.

4. A rectification column as defined in claim 3 wherein said distance isabout mm.

5. In a rectification column comprising a housing having at least onehorizontal dimension greater than its vertical dimension, theimprovement which comprises an array of vertically spaced generallyhorizontal and substantially rectangular rectification plates mounted insaid housing and provided with openings constituting said plates asrespective rectification stages, said rectification plates beingcomposed of thicker and thinner plates with said thinner plates beingdisposed between the thicker plates, the thicker plates being secured toopposite walls of the housing along opposite edges of the thicker plateswhere by said thicker plates structurally reinforce said housing, saidopposite walls of said housing being formed with outwardly convexelongated metallic strips bridging corresponding pairs of adjacent edgesof the thick plates and welded together therealong.

5 6. The improvement defined in claim 5 wherein said walls are providedwith flat vertical inner wall members, said strips being welded to saidfiat 'Wall members contiguously along longitudinal edges of the strips.

References Cited Harris 261-113 XR Newhall 261113 XR Dennis 62-42 Becker62-42 NOR-MAN YUDKOFF, Primary Examiner.

V. W. PRETKA, Assistant Examiner.

Bardo 202-158 XR 10 202158; 261113 US. Cl. X,'R.

